1. Field of the Invention
This invention relates to a particulate composition that contains microcrystalline cellulose and calcium carbonate and which is useful as an excipient in pharmaceutical formulations.
More particularly, microcrystalline cellulose and calcium carbonate are processed together in an aqueous medium and dried to yield a particulate excipient product.
2. Description of the Prior Art
Microcrystalline cellulose is a purified, partially depolymerized cellulose that is prepared by treating alpha cellulose, in the form of a pulp manufactured from fibrous plant material, with mineral acids. It is a white, odorless, tasteless, relatively free flowing powder that is insoluble in water, organic solvents, dilute alkalis and dilute acids. U.S. Pat. Nos. 2,978,446 issued to Battista et al. and 3,146,168 issued to Battista are basic patents describing microcrystalline cellulose and its manufacature; the latter patent concerns microcrystalline cellulose for pharmaceutical applications.
Microcrystalline cellulose finds widespread use as a pharmaceutical excipient, an inactive (non-drug) ingredient in pharmaceutical formulations. Its inherent compressibility characteristics account for its popularity as a pharmaceutical excipient, since good binding and disintegration properties are obtained with microcrystalline cellulose when used in direct compression tablet formulations.
Compared to other tablet additives like partially pregelatinized cornstarch, lactose, and dicalcium phosphate, microcrystalline cellulose exhibits superior compressibility and disintegration properties. Unlike these additives, microcrystalline cellulose is relatively costly to manufacture; this limits its use in price-sensitive formulations like vitamins.
A lower cost excipient which has tabletting characteristics similar to those of microcrystalline cellulose would satisfy a need for an economical excipient with good performance that is desired by the vitamin market.
Physical blends of microcrystalline cellulose with starch, lactose of dicalcium phosphate, do not provide the desired performance characteristics. Microcrystalline cellulose coprocessed with either starch or calcium sulfate, as described by Schwartz et al. in Drug & Cosmetic Industry 118, 60 (April 1976) and 114, 44 (April 1974), offers direct compression tabletting performance that falls short of that for microcrystalline cellulose alone.
The present invention accomplishes this objective with microcrystalline cellulose that is coprocessed with a second, inexpensive component in a manner that yields a particulate product with unexpectedly good excipient performance characteristics.